And before people read this the wrong way... I mean a second camera alongside. I have an FX DSLR, but use a sony NEX5 if I want to go light, but I have no problem sacrificing the wide end at those times.

What I mean to say it: DSLR + light + small = oxymoron

Maybe they will come out with a 16 or 18mm DX that can stay small, but 10-12mm will be bigger and heavier, even on DX.